This invention relates to a new and improved method and apparatus for applying air pressure pulses to a person's respiratory system to assist ventilation and respiration.
It has been found that persons with various respiratory problems and illnesses can be benefitted by application to the person's respiratory system of rapid, positive pressure pulses of oxygen and air. This type of "ventilation" is superior to the more conventional method of ventilation which consisted of application of relatively large volumes of oxygen and air to a person at frequencies which coincided substantially with the inhalation frequency of the person. Some of the problems with this conventional technique are that those areas of the lung with the least blood perfusion may be preferentially ventilated, added resistance to blood flow into the thorax and pulmonary capillaries is imposed, and blood pressure is oftentimes altered. In addition, the decreased compliance of the lungs of those persons who suffer from respiratory distress syndrome causes high intrapulmonary pressures to be necessary during the application of the oxygen-air pulses. These high pressures oftentimes produce the side affects of pneumothorax, cerebral hemorrhage and broncho-pulmonary dysplasia, all of which are life threatening and debilitating.
Two prior art methods of applying positive pressure pulses of gas to a patient at a higher than normal rate of inhalation and exhalation are disclosed in U.S. Pat. No. 4,155,356 and U.S. Pat. No. 2,918,917. In the first mentioned U.S. Pat. No. 4,155,356, the object of the method described is to alleviate respiratory problems caused from a collapsed lung passageway which, for example, may result from emphysema. The apparatus and method of U.S. Pat. No. 4,155,356 provide for supplying a series of pressure pulses to the air passageway in question, with the pulses having a certain defined wave form and frequency rate. Further, the person on which the method is used is generally able to inhale but not exhale and so the method is used to assist exhalation only. Thus, U.S. Pat. No. 4,155,356 is not directed strictly to assisting respiration--both inhalation and exhalation--to alleviate respiratory problems.
U.S. Pat. No. 2,918,917 discloses apparatus for "vibrating portions of a patient's airway" at a rate which is greater than the patient's normal rate of inhalation and exhalation. The purpose of this is to exercise and massage the airway and associated organs to thus loosen and remove mucous therefrom. It was also stated in the patent that it was believed that vibrating portions of a patient's airway aided in the breathing function by circulating the gas more thoroughly to and from the walls of the lungs.
In co-pending application, Ser. No. 322,742, now U.S. Pat. No. 4,481,944, a system is described for applying a series of high pressure air pulses to a person's respiratory system, with the frequency of the pulses being varied over some range encompassing the natural or resonant frequency of the person's respiratory system. This system achieves a degree of ventilation of a person's respiratory system not heretofore achieved.
The present invention improves upon and simplifies the above-described system by providing mechanisms which may be readily serviced and replaced, and which delivers high energy density positive pressure pulses to a patient to better ventilate the patient's respiratory system.